[antlr-interest] full LL(K) vs linear approximation?

mzukowski at yci.com mzukowski at yci.com
Mon Mar 17 12:02:41 PST 2003


It also takes longer to do the analysis for LL(K) than for LALL(K).  The
main reason it isn't done is because of laziness; LALL(K) works most of the
time.  The ideal is to detect those situations where LALL(K) fails and then
do full LL(K) analysis.  This has some pretty big repercussions on the
current implementation of the LALL(K) analysis algorithm, which needs to be
reworked anyhow to accomodate hoisting of semantic predicates.

Speed is also a major issue in the generated parser.  The hybrid approach
will be the best win.  Generating LL(K) decision code is straightforward.

Monty

-----Original Message-----
From: Albert Huh [mailto:albert.huh at embarcadero-ca.com]
Sent: Monday, March 17, 2003 11:03 AM
To: antlr-interest at yahoogroups.com
Subject: [antlr-interest] full LL(K) vs linear approximation?


does anybody know exactly why full LL(k) isn't done in antlr?

is it due to speed with larger k-values?  (each decision will take k^2
comparisions as opposed to just k comparisions?)

is it harder to generate full LL(k) analysis code?

 

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